Experimental model validation and predictive control strategy for an industrial fire-tube boiler. (1st December 2022)

• Record Type: Journal Article
• Authors: Ferrarini, Luca; Rastegarpour, Soroush; Landi, Antonio
• Is Part Of: Thermal science and engineering progress. Volume 36(2023)
• Publication Date: 2022-12-01
• Subjects: Fire-tube boilers -- Shrink and swell phenomenon -- Predictive control -- Cascade control structure -- Energy efficiency; Heat engineering -- Periodicals; Heat engineering; Thermodynamics; Periodicals; 621.402
• DOI: 10.1016/j.tsep.2022.101482
• Languages: English
• ISSNs: 2451-9049

Abstract

Abstract: This paper presents a flexible control structure for fire-tube boilers based on a suitable integration of the typical decentralized PI control structure and model predictive control technique. First, a dynamic nonlinear reference model of the fire-tube boiler is developed combining models available in the technical literature, based on first principle laws. The overall system model is considered as a gray-box model, and it has been validated with real data. Then, a suitable control-oriented model is derived out of the nonlinear reference model, in order to design a hybrid cascade MPC-PI control structure capable of guaranteeing stability, improving performances and enforcing real-time constraints. The flexibility of such a structure can be exploited to impose different types of functional behavior to the boiler itself, from the performance-related ones to the efficiency increase ones. While the reference non-linear model is large and detailed, the control-oriented one is simplified so that a few process parameters are identified to reduce dramatically the implementation in the MPC controller hardware and software framework. A sensitivity analysis with respect to these process parameters highlights the robustness and easy implementation of such a strategy. Two MPC configurations have been developed and tested in simulation over the validated boiler model. Then, a customized algorithm has been developed to understand a massive quantization phenomenon on the boiler pressure measurement. Finally, a test session conducted on a real fire-tube boiler quantifies the performance benefits of one configuration of the MPC-PI control structure with respect to the PI control. Highlights: Tuning of a dynamic nonlinear reference model of the fire-tube boilers with real data. A hybrid cascade MPC-decentralized PID control structure, easily tunable. Sensitivity analysis to test the robustness and easy implementation of such a control strategy. A customized algorithm to reject a massive quantization on the boiler pressure measurement. Implementation of the optimal control strategy and test session on a real fire-tube boiler.